The invention relates to a control device for reducing electrical malfunctions in a network which are caused by torque fluctuations of an electric motor, in particular flicker. The invention also relates to a system having a control device of this type and to a method for reducing electrical malfunctions which are caused by torque fluctuations of an electric motor, in particular flicker, in a network by means of a control device of this type.
One cause of malfunctions, for example flicker, in a network is torque fluctuations in drive devices which are electrically connected to the network. In a drive device, an electric motor which is supplied via a converter is coupled to a mechanical load or a mechanical source. Malfunctions can arise when the mechanical load, for example a piston compressor, or the mechanical source, such as an internal combustion engine has a varying torque pattern. This leads to variations in the network current which can then cause malfunctions in the network. The electric motor can be operated either as a motor, so that it converts electrical energy into mechanical energy in order thereby to drive a load, or it can be operated as a generator when it converts mechanical energy into electrical energy in order thereby to generate electrical energy. The converter serves to control the energy flow. A converter control system is associated with the converter, inter alia, for receiving target value signals. It can be arranged in the immediate vicinity of, particularly in a common switchgear cabinet together with, the converter or spatially separate therefrom. An uneven mechanical loading on the motor shaft, which is caused, for example, by the operation of a piston compressor, leads to an uneven electrical loading on the network, which can manifest itself in the form of network malfunctions such as flicker. The uneven mechanical loading of the electrical motor can be buffered and reduced in that a large inertial mass is used on the motor shaft. This reduces the interfering effects on the electrical side of the electric motor. However, the inertial mass increases the structural volume, the weight and thus also the costs of the motor unit, sometimes even significantly.
It is an object of the invention to minimize and ideally to eliminate, by simple and inexpensive means, electrical malfunctions arising from torque fluctuations during operation of a load or a source at an electric motor which is electrically supplied by means of a converter connected to the network.